Shielded coil



Sept. 17, 1946. H o, BERG sHIELDEn con. Filed April 1o, 1943 sept. 17, 1946. .4131.55.26-- 2,407,916

SHIELDED COIL Filed April 10, 1945 2 Sheets-Sheet 2 Patented Sept. 17, 1946 SHIELDED COIL Howard 0. Berg, Chicago, Ill., assignor to Stewart-Warner Corporation, Chicago, Ill., a corporation of Virginia Application April 10, 1943, Serial No. 482,528

(Cl. Z50-16) 5 Claims. l

My invention relates to shielded coils and more particularly to permeability tuned intermediate frequency transformers.

An object of my invention is to provide a new and improved shielded coil which is ci simple construction and more easily assembled than those heretofore known.

Another object of my invention is to provide a shielded coil which is cheaper to manufacture than the coils of the prior art.

Another object of my invention is to provide a shielded coil which is more eiiicient for all conditions of temperature and humidity than are the prior art coils.

Other objects and advantages will become apparent as the description proceeds.

In the drawings:

Fig. 1 is a longitudinal, sectional View through a shielded coil embodying a preferred form of my invention;

Fig. 2 is an end view of the coil oi Fig. 1 loolzing in the direction of the arrows ii-Z of this figure;

Fig. 3 is an end view of the coil shown in Fig. 1 and is taken looking in the direction of the arrows 3 3 of Fig. 1;

Fig, 4 is a transverse, sectional view taken on the line 4 4 of Fig. 1;

Fig. 5 is a side elevation of the coil shown in Fig. 1;

Fig. 6 is a partial, transverse, sectional View showing a detail of construction and is taken on the line of Fig. 3;

Fig. '7 is a longitudinal sectional view of the tube, electrical coils and condensers.

Fig. 8 is a wiring diagram showing the electrical connections for part of a typical radio circuit incorporating my invention.

In the drawings I have illustrated a thin walled tube l of Bakelite, ceramic or other suitable insulating and non-magnetic material on which the electrical coils i2 and I4 are wound. This tube is clamped between a pair of end plates Iii and I8 of Bakelite or other suitable insulating and non-magnetic material which serve to center the tube lil and electrical coils l2 and ill in spaced relation to a sleeve 20 preferably formed of iro-n dust and a suitable binder, such as pow dered Bakelite.

The electrical coil i2 is provided with an iron dust core 22 mounted on a screw 24 threaded in the end plate I6. The screw 24 has a kerf Z5 in its exposed end to facilitate adjustment oi the core 22 lengthwise of the tube lil. The electrical coil I4 is similarly provided with an iron 2 dust core 2S mounted on a screw 35i threaded in the Bakelite end i8 and provided with an eX* ternal kerf 32 to facilitate adjustment of the core lengthwise of the tube l0.

The sleeve 2@ is enclosed in a tubular metal shield 34 having an in-turned end Sii which over" lies the end plate it, and irl-turned fingers it which overlie the end plate it whereby the shield fili secures and holds the several parts in assembled relationship. L-shaped terminals ft2 are attached to the end plate i8 by rivets dfi. or in any other suitable manner, and the leads for the electrical coils i2 and i4 are soldered to the inner ends of these rivets, as indicated in l, there being four terminals 42 and a separate electrical coil lead soldered cr otherwise secured to the rivet for each terminal.

In Fig. '7 1 have illustrated more clearly the arrangement of the electrical condensers on the tube IE). At one end of the tube it lrns ii and 52 of copper or other suitable metal are sputtered ory otherwise formed on the inside and outside of the tube. Therlm Eil ds around the end of the tube and a short c tance down the outside thereof to permit an electrical conductor to be soldered or otherwise attached to this lm. A gap iii is located between the a .l-- jacent ends or the films so that each film forms one plate of a condenser the tube constitutes the dielectric between these plates.

The other end of the tube 113 is similarly provided with inner and outer sputtered :films 55 and 5B, respectively, which form the plates of a second condenser. These condensers are connected in parallel with the electrical coils I2 and I4, as indicated in Fig. 3 of the drawings, and where the tube lil is used, it is unnecessary to provide my shielded coil with outside condensers as is the usual practice.

This Fig. 8 shows part of a typical radio circuit embodying my shielded. coil. In this gure the electrical coil i2 and condenser Eil-52 are arranged in parallel and interposed between the plate @t of a radio frequency tube e2 and the positive pole of a B battery or its equivalent. The coil lliand condenser {i5-siii are also'in parallel and are interposed between the grid 6d of a second radio frequency tube 56 and a grounded terminal indicated at 6K3.

In assembling my new and improved coil, I have found it most advantageous to form two sub-assemblies which are subsequently brought together to make the completed shielded coil. One such sub-assembly is formed by inserting screw 24 in end plate i6 and adjusting the screw to bring the core 22 to approximately the proper position. Thereafter sleeve 2E] is aflixed to end plate i6 by applying a suitable cement, such as Glyptal, between the contacting surfaces of these parts, whereupon the end plate Iii, core 22 and sleeve E are inserted in shield 34 to form one sub-assembly.

The other sub-asse1nbly is formed by inserting screw 3S into end plate I8, attaching tube l0 to end plate i8 by means of Glyptal, or other suitable cement, and attaching the leads for the electrical coils-cr for the electrical coils and condensers, as the case may loe-to the terminal rivets M to complete the second sub-assembly. This second sub-assembly is then inserted. in the sleeve 2U and shield 34 and the iingers 40 of this shield are then bent over to the position shown in Fig. l to complete the entire assembly.

I have found that my new and improved shielded coil is particularly efdcient under all conditions of temperature and humidity where the interior of the coil is sealed against atmosphere. This can be effective by placing Glyptal or other cement between the engaging surfaces or the end plates and sleeve and by placing cement around the screws il!! and 3i] at the outer surfaces of the end plates i6 and i8. These screws should. only be sealed after the final adjustment of the cores 22 and 28 has been coinpleted.

While I have described my invention as being particularly adapted for intermediate frequency transformers, my invention is not limited to such use and shielded coils embodying my invention may be used for other purposes. My invention is not limited to the particular details shown and described, but may assume numerous other forms and includes all variations and modiiications falling within the scope of the appended claims.

I claim:

l. A shielded coil of the class described, comprising a non-.magnetic and insulating tube having an inner and an outer metallic film at each end thereof, each inner iilm and its adjacent outer film forming a separate electrical condenser, electrical coils wound on said tube on the uncoated portion thereof, an iron dust core for each of said coils, said cores being movable lengthwise of said tube, an iron dust sleeve enclosing said coils and tube, end plates maintaining said tube and sleeve in spaced co-axial relationship, and a metal shield surrounding said sleeve and having portions overlying said end plates.

2. A shielded coil of the class described, comprising a dielectric tube having an inner and an outer copper lm at each end thereof, each inner film and its adjacent outer film forming a separate electrical condenser, electrical coils wound on said tube on the uncoated portion thereof, a core for each of said coils, said cores being movable lengthwise of said tube, a magnetic sleeve enclosing said coils and tube, end plates maintaining said tube and sleeve in spaced co-axial relationship, and a metal shield surrounding said sleeve.

3. A shielded coil of the class described, comprising an insulating and non-magnetic tube having an inner and an outer metallic film at each end thereof, each inner film and its adjacent outer film forming a separate electrical condenser, an electrical coil wound on said tube on the uncoated portion thereof, an iron dust core for said coil, said core being movable lengthwise of said tube, an iron dust sleeve enclosing coil and tube, means maintaining said tube and sleeve in spaced co-axial relationship, and a metal shield surrounding said sleeve and hav*- ing portions overlying said end plates.

A shielded coil of the class described, comprising an insulating and non-magnetic tube having an inner and an outer metallic film at each end thereof, each inner film and its adjacent outer film forming a separate electrical condenser, electrical coils wound on said tube on the uncoated portion thereof, an iron dust core for each of said coils, an iron dust sleeve enclosing said coils and tube, end plates maintainf ing said tube and sleeve in spaced co-axial relationship, and a metal shield surrounding said sleeve and having portions overlying said end plates.

5. A shielded coil of the class described, comprising a ceramic tube having an inner and an outer metallic film at each end thereof, each inner film and its adjacent outer film forming a separate electrical condenser, electrical coils wound on said tube on the uncoated portion thereof, an iron dust core for each of said coils, said cores being movable lengthwise of said tube, an iron dust sleeve enclosing said coils and tube, end plates sealing the ends of said sleeve, a metal shield surrounding said sleeve and having portions overlying said end plates, and terminals for said coils and condensers attached to an end plate.

HOWARD O. BERG. 

